The present invention broadly relates to gear-cutting and, more specifically, pertains to a new and improved method and apparatus for eliminating undulation errors in commercially produced gears.
Generally speaking, the method of the present invention is for eliminating undulation errors on gear-tooth flanks when fabricating gears on a production gear-fabricating machine, wherein a generating motion corresponding to a desired involute profile is induced between a gear-fabricating tool and a gear-tooth flank by rotating a rotary table upon which a gear being fabricated is fixed at a predetermined angular velocity and by simultaneously translating the rotary table at a predetermined linear velocity.
The apparatus of the present invention for eliminating undulation errors on gear-tooth flanks when fabricating gears in a production gear-fabricating machine having a rotary table for the gear to be fabricated comprises a first drive mechanism associated with the rotary table for rotating the rotary table at a predetermined angular velocity together with the gear to be fabricated and a second drive mechanism associated with the rotary table for simultaneously translating the rotary table at a predetermined linear velocity together with the gear to be fabricated for the purpose of inducing a generating motion corresponding to a desired involute profile between at least one gear-fabricating tool and at least one gear-tooth flank. It also comprises measurement devices associated with the rotary table for monitoring the angular and linear velocities.
It is known, for instance from the technical journal "Werkstatt und Betrieb", No. 113 (1980) 2, pages 97 to 100, that the gear-tooth flanks of gears cut by the generating process have corrugated or undulating irregularities. These corrugations or undulations are particularly apparent in helical gears and result principally from errors of the rotary drive worm and of the linear drive spindle which induce the generating motion by imparting a rotary motion with a predetermined speed and simultaneously a translatory motion with a predetermined speed to the rotary table of the machine. The periodic, relatively long-wave and therefore very dangerous corrugations or undulations are due to errors of eccentricity, aplanarity, run-out or wobble, axial play and angular velocity as well as errors of helical pitch and pressure angle of the rotary drive worm and of the translatory drive spindle.
In general, all of the gearing errors of the rotary table drive are effective to a greater or lesser extent. Worm drives can also have circular pitch errors and errors of journaling the worm (eccentricity). These errors in the rotary table drive result in periodical corrugations or undulations in the direction of the profile (tooth height) in the finished gear and, in helical gears, also in periodical corrugations or undulations in the direction of the tooth width (cf. W1 and W2 in FIG. 1).
Since the periodical corrugation (the so-called undulation) is continuously periodic and does not just arise sporadically upon the gear periphery, it constitutes a particularly onerous source of generation of vibrations and noise.
In the present state-of-the-art (cf. the aforementioned technical journal) attempts are being made to prevent gear-tooth corrugations or undulations by means of as exact as possible a machining of all important drive components of the production machine. That is, however, only possible within limitations, since the tolerances maintained on large gears in the present state-of-the-art are already so small that they can only be detected with great difficulty by measurement technology.